Composition for electrolytes for electrical etching.



STATES PATENT OFFICE.

- JOSEPH HENRY WEEKS, 0F RUTLEDGE, PENNSYLVANIA, ASSIGNOR T0 JACKSON S.WEEKS, OF DELAWARE COUNTY, PENNSYLVANIA, AND RAYMOND M. WEEKS, 0F

PHILADELPHIA, PENNSYLVANIA, TRUSTEES.

COMPOSITION FOR ELECTROLYTES FOR ELECTRICAL ETCHING.

1,273,432. No Drawing.

To all whom it may concern Be it known that I, JOSEPH H. WEEKS, acitizen of the United States, residing at Rutledge, in the county ofDelaware and State of Pennsylvania, have invented certain new and usefulImprovements in Composition for Electrolytes for Electrical Etching, ofwhich the following is a specification, reference being had therein tothe accompanying drawing.

My invention has for its object the production of an improvedelectrolyte for use in electrical etching of metals.

The general subject matter to which this invention relates is discussedin my prior applications, Serial Numbers 88,362, 108,232, and 119,548,filed respectively April 1, 1916, July 8, 1916, and September 11, 1916.In the first of said applications, I have disclosed a method, apparatus,and certain compositions for electrolytes intended to be used therein;in the second application, I have described and claimed a process andcomposition, and in the third application, I have described and claimedcertain improved apparatus. The electrolyte which I shall hereinafterset forth is adapted for use in the aforesaid processes, andwith theaforesaid apparatus, although it is not necessarily limited thereto andmay be employed in other connections, and for other metals or alloys ofmetals than those therein specifically described.

In the prior applications referred to, I have set forth a method ofetching plates in which a resistant image is produced on a plate, eitherby means of ink and powder, which is wellknown in the art, or by meansof a special gelatin albumen enamel of my own invention. The plate soprepared is suspended in a suitablebath or solution and connected so asto form the anode terminal of a circuit supplied with current ofsuitable .voltage to produce the desired amperage or volume of currentflow per unit area of anode. The cathode terminal, which is alsoimmersed in the bath or solution, may be of various types and of variousmaterials. In my application I have described carbon cathodes, and haveset forth means for keeping. the surface of the plate clean so that 1tSpecification of Letters Patent.

Patented July 23, 1918.

Application filed April 4, 1917. Serial No. 159,778.

shall be completely and uniformly exposed to the electrolytic action ofthe current, and for keeping the cathodes clean, and for pre- 'ventingundercutting ofthe edges of the image or lines on the plate.

The problems to be met are different from those presented in theelectro-plating art, because, in the latter, it is the deposition ofmetal which concerns the operator, and which must be even and regular,as well as reasonably rapid; whereas, in the present cases, it is theremoval of the metal by the current into or through the solution, whichmust be properly regulated, and this to a much greater degree ofaccuracy and uniformlty than is necessary in the art of depositlon.

In my experimental work, which has extended over a considerable period,and in the course of which the present invention and the othershereinbefore referred to have been produced, I have found that thecomposition of the electrolyte plays a very considerable part, not onlyin the regulation of the action on the plate, but in the uniformity forabsorbing and transferring the electrically displaced metal from theplate without soon becoming saturated or clogged; third, no tendency tofoul or coat or form spots upon the plate, which would impede the freepassage of the current and thereby mar the engraving; fourth, notendency, or a reduced tendency, to foul and form sludge upon thecathode surface in such manner that it cannot be readily removed; andfifth, such elements and such a balance of forces and properties thatits suificiency will remain unimpaired for a considerable period of timeand use.

The solution which I shall hereinafter set forth has for its principalactive element an oxalate or oxalates, either alone or in combination.with certain other substances, and meets these conditions.

. tions above referred to, and many others.

The metals most commonly employed in the engravin art are copper, brass,steel, and zinc, an the plates are employed for printing, stamping, andfor other purposes. In addition to the engraving of steel printingplates both in relief and intaglio, the manufacture of steel dies andplates for stamping metals is, in itself, very important, and by myprocess, and with my solutions, I can produce such dies and plates inmuch less time, and with much less expense, than where they are cut byhand according to the old ractice. Where the plates are to be emp oyedfor printing, my invention is specially important at the present time,because of the scarcity of high grade paper, and the necessity forhaving perfect printing plates in order to produce satisfactory resultson the cheap grade of paper now commonly employed.

Electrolytes are prepared, for the greatest efficiency and economy, forthe particular metals to be etched. Wherever practicable, a combinationis used' in which the plate to be etched is kept clean without wiping.This is especially requisite in very delicate work, as frequent wipingwould tend to injure the material of the image. In coarse work, this isrelatively immaterial, and an electrolyte involving wiping of the platemay easily be used, and would be used where it is cheaper to prepare, orproduces a speedier action. The cleanliness of the cathode is nextpreferable, as involving less labor in keeping clean, or as renderingthat portion of my apparatus having movable brushes unnecessary, with aconsequent saving in power used thereby. For the reasons stated, some ofmy formulae do not give both a clean cathode and a clean anode.

The various use of chlorids, sulfates and oxalates, with or withoutacids, is in some instances to secure anode .or cathode platecleanliness or both, and to obtain electrolytes which shall form thebest chemical combinations in themselves and with the anode, shall havethe longest life, and produce the smoothest etching, i. e.,to avoidrough grainy etching on either the sides of the lines or the bottom, andfurther, to secure a desirable speed which will admit of commercialetching of the various metals with practically the same electric currentdensity. The value of this last is obvious, particularly where onedynamo or battery set is employed to supply urrent for the etching ofdifierent metals in separate tanks without the employment of resistance.

An acid condition is desirable in all electrolytes to give stability tothe same and to increase the conductivity. If the constituent salts donot render the electrolyte acid or sufficiently acid for these purposes,an acid should be added. Some excellent electrolytes would promptlyseparate under electrolysis and promptly become useless were it not forthe addition of the acid. Even if this does not occur the life of theelectrolyte is shorter without acid and its conductivity less. Furtherin many cases the presence of an acid prevents precipitations in theelectrolyte or on the cathodeor on theanode or performs two or all ofthese functions.

In some combinations where the ordinary acids do not keep the cathode orthe anode clean or prevent precipitations in the bath, this may in someinstances be partly or wholly accomplished by the addition of a chromiumsalt, or by whatv is generally termed chromi acid (usually potassiumdichromate solution acted upon by sulfuric acid), although the actionherein stated does not depend on the sulfuric acid in the chromic acidas that might independently be present in or added to the electrolyteunder the head of acids. The chromium salts are also employed on accountof their tendency to a, smooth surface in the anode where it is foundthat ordinarily the surface is rough, smoothness of the anode beingusually a desirable feature.

Specifically stated, the solution to be claimed herein consistsessentially of one or more of the oxalates of aluminum, ammonium,cadmium, calcium, chromium, cobalt,

copper, iron, lithium, magnesium, manganese, nickel, potassium, tin, andzinc.

While the essence of the invention is the use of a suitable oxalate, Imay and do employ more than one, in combination, when required, but itis obvious that. only those which will properly mix or combine can besimultaneously employed.

WVith the oxalates, I may combine a chlorid or a chromium salt, with orwithout the addition of acid. I may also employ, as an additionalelement, a small quantity of perchlorid, such as the per-chlorid ofiron, containing an excess of acid. This may be used in lieu of one ormore of the chlorids, and in such case, no other acid is usuallynecessary. The principal function of the separate acid, if added, is toincrease the conductivity and prevent any decrease in current densityand tends in most cases to keep the face of the plate clean and toprevent disintegration of the solution.

As an example of a specific solution which I have found very useful withsteel and other metals, I may give the following:

Iron oxalate in water to make saturated solution 5 oz. (fluid) Nitricacid C. P 3; oz. (fluid) In certain cases, I have found it of advantageto combine an oxalte with a sulfate in an aqueous solution, with orwithout acid. As an example thereof, I may give the following:

As an example of a solution in which a chlorid and an acid are employed,I may give the following:

Iron oxalate in water to make saturated solution 5 oz. (fluid) Iron(per) chlorid solution at about 42 Baum which is acid 2 oz. (fluid) (Ifneutral iron chlorid e ployed, muriatic acid to make equivalent of aboveis als added.)

The following are examples in which chromium salts, chlorids, tartratesand acid are usefully employed:

Sodium oxalate saturated solution (in Water) C. P. nitric acid to clearand slight excess. 1 Saturated solution dichromate of potassium (inwater) Q; oz.

240 grains Potassium .oxalate Water Ammonium chlorid solution It is tobe noted that, in the claims, where I mention a chlorid and a sulfate, Iinclude in that expression a chlorid and two or more sulfates, two ormore chlorids and a sulfate or two or more chlorids and two or moresulfates.

Having thus described my invention what cium, cadmium, magnesium, iron,potassium,

sodium or strontium, dissolved in water.

An electrolyte composed of one or more of the oxalates of ammonium,barium, calcium, cadmium, magnesium, iron, potassium, sodium orstrontium, dissolved in Water, and an acid.

3. An electrolyte composed of one or more of the oxalates of ammonium,barium, calcium, cadmium, magnesium, iron, potassium, sodium orstrontium, dissolved in water, together with a tartrate and an acid.

4. An electrolyte composed of one or more of the oxalates of ammonium,barium, calcium, cadmium, magnesium, iron, potassium, sodium orstrontium, dissolved in water, together with a sulfate and an acid.

5. An electrolyte composed of one or more of the oxalates of ammonium,barium, calcium, cadmium, magnesium, iron, potassium, sodium orstrontium, dissolved in water, together with a chlorid and an acid.

6. An electrolyte composed of one or more of the oxalates of ammonium,barium, calcium, cadmium, magnesium, iron, potassium, sodium orstrontium, dissolved in water, together with a sulfate, a chlorid and anacid.

7. An electrolyte composed of one or more of the oxalates of ammonium,barium, calcium, cadmium, magnesium, iron, potassium, sodium orstrontium, dissolved in water together with a tartrate, a sulfate and anacid.

8. An electrolyte composed of one or more of the oxalates of ammonium,barium, calcium, cadmium, magnesium, iron, potassium, sodium orstrontium, dissolved in water, to-

gether with a tartrate, a chlorid and an acid.

9. An electrolyte composed of one of more of the oxalates of ammonium,barium, calcium, cadmium, magnesium, iron, potassium, sodium orstrontium, dissolved in water, together with a sulfate, a chlorid, atartrate, and an acid.

In testimon whereof I aflix my signature.

J SEPH HENRY WEEKS.

Witness:

' Tnos. J. HUNT.

